The muddled kumquat (or, in a pinch, a Clementine or other flavorful orange) and lime bring the citrus notes. acid balance, and a bit of oomph from the peel. The Fee's Whiskey Barrel Aged bitters adds a touch of bitter spicy depth. The resulting concoction is sort of a Batida -- a flavored Caiprinha, but with more complexity than one normally expects from Brazil's most famous drink.